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Date: Tue, 17 Apr 2012 09:36:09 +0000
From: "Chen, Dennis (SRDC SW)" <Dennis1.Chen@....com>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: Ingo Molnar <mingo@...nel.org>,
"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
"peterz@...radead.org" <peterz@...radead.org>,
Paul Mackerras <paulus@...ba.org>,
Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: A quick view of the performance benchmark for semaphore-like and
mutex
Just as a quick & rough test, with below changes based on mutex (almost the same as semaphore):
--- /home/dennis/Linux/linux-3.3.2-sem/kernel/mutex.c 2012-04-17 14:59:49.823177615 +0800
+++ ./mutex.c 2012-04-17 17:00:12.963059284 +0800
@@ -140,6 +140,7 @@ __mutex_lock_common(struct mutex *lock,
preempt_disable();
mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
+#if 0
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
/*
* Optimistic spinning.
@@ -195,6 +196,7 @@ __mutex_lock_common(struct mutex *lock,
arch_mutex_cpu_relax();
}
#endif
+#endif
spin_lock_mutex(&lock->wait_lock, flags);
debug_mutex_lock_common(lock, &waiter);
#perf record -a perf bench locking mutex -p 8 -t 3000
The benchmark result BEFORE (mutex)
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
round 1:
Total duration 39868 s 536095 us
real: 15.89 s
user: 0.00
sys: 0.31
Events: 64K cycles
20.18% perf [kernel.kallsyms] [k] __mutex_lock_slowpath
8.41% perf [kernel.kallsyms] [k] _raw_spin_lock
8.00% perf [kernel.kallsyms] [k] mutex_unlock
5.29% perf [kernel.kallsyms] [k] mutex_lock
2.88% perf [kernel.kallsyms] [k] link_path_walk
2.56% perf [kernel.kallsyms] [k] __mutex_unlock_slowpath
2.31% perf [kernel.kallsyms] [k] mutex_spin_on_owner
2.29% perf [kernel.kallsyms] [k] _raw_spin_lock_irqsave
1.68% perf [kernel.kallsyms] [k] __d_lookup
1.33% perf [kernel.kallsyms] [k] dput
1.33% perf [kernel.kallsyms] [k] clear_page_c
1.06% perf [kernel.kallsyms] [k] __strncpy_from_user
1.04% perf [kernel.kallsyms] [k] do_lookup
...
-------------------------------------------------------------------------------------
round 2:
Total duration 39748 s 176410 us
real: 15.92 s
user: 0.00
sys: 0.32
Events: 63K cycles
19.68% perf [kernel.kallsyms] [k] __mutex_lock_slowpath
8.53% perf [kernel.kallsyms] [k] _raw_spin_lock
7.74% perf [kernel.kallsyms] [k] mutex_unlock
5.09% perf [kernel.kallsyms] [k] mutex_lock
3.06% perf [kernel.kallsyms] [k] link_path_walk
2.54% perf [kernel.kallsyms] [k] __mutex_unlock_slowpath
2.31% perf [kernel.kallsyms] [k] mutex_spin_on_owner
2.30% perf [kernel.kallsyms] [k] _raw_spin_lock_irqsave
1.76% perf [kernel.kallsyms] [k] __d_lookup
1.46% perf [kernel.kallsyms] [k] clear_page_c
1.31% perf [kernel.kallsyms] [k] dput
1.10% perf [kernel.kallsyms] [k] __strncpy_from_user
1.08% perf [kernel.kallsyms] [k] do_lookup
...
-------------------------------------------------------------------------------------
round 3:
Total duration 40047 s 394364 us
real: 15.59 s
user: 0.00
sys: 0.30
Events: 58K cycles
19.18% perf [kernel.kallsyms] [k] __mutex_lock_slowpath
8.68% perf [kernel.kallsyms] [k] _raw_spin_lock
7.80% perf [kernel.kallsyms] [k] mutex_unlock
5.24% perf [kernel.kallsyms] [k] mutex_lock
3.22% perf [kernel.kallsyms] [k] link_path_walk
2.57% perf [kernel.kallsyms] [k] __mutex_unlock_slowpath
2.38% perf [kernel.kallsyms] [k] _raw_spin_lock_irqsave
2.13% perf [kernel.kallsyms] [k] mutex_spin_on_owner
1.79% perf [kernel.kallsyms] [k] __d_lookup
1.54% perf [kernel.kallsyms] [k] clear_page_c
1.34% perf [kernel.kallsyms] [k] dput
1.12% perf [kernel.kallsyms] [k] do_lookup
1.04% perf [kernel.kallsyms] [k] __strncpy_from_user
1.02% perf [kernel.kallsyms] [k] system_call
1.02% perf [kernel.kallsyms] [k] get_page_from_freelist
...
The benchmark result AFTER (remove the optimization part of mutex)
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
round 1:
Total duration 66319 s 868892 us
real: 23.16 s
user: 0.00
sys: 0.29
Events: 81K cycles
6.30% perf [kernel.kallsyms] [k] _raw_spin_lock
3.13% perf [kernel.kallsyms] [k] mutex_unlock
3.09% perf [kernel.kallsyms] [k] mutex_lock
3.07% perf [kernel.kallsyms] [k] link_path_walk
2.66% swapper [kernel.kallsyms] [k] intel_idle
2.21% perf [kernel.kallsyms] [k] __d_lookup
1.80% perf [kernel.kallsyms] [k] clear_page_c
1.58% perf [kernel.kallsyms] [k] system_call
1.56% perf [kernel.kallsyms] [k] __strncpy_from_user
1.53% perf [kernel.kallsyms] [k] do_lookup
1.47% perf [kernel.kallsyms] [k] dput
1.43% perf [kernel.kallsyms] [k] get_page_from_freelist
1.28% perf libc-2.13.so [.] 0xa99f6
1.19% swapper [kernel.kallsyms] [k] _raw_spin_lock_irqsave
1.15% perf [kernel.kallsyms] [k] vfsmount_lock_local_lock
1.12% perf [kernel.kallsyms] [k] kfree
...
-------------------------------------------------------------------------------------
round 2:
Total duration 67448 s 392232 us
real: 23.21 s
user: 0.00
sys: 0.29
Events: 82K cycles
6.23% perf [kernel.kallsyms] [k] _raw_spin_lock
3.23% perf [kernel.kallsyms] [k] mutex_unlock
3.10% perf [kernel.kallsyms] [k] mutex_lock
3.10% perf [kernel.kallsyms] [k] link_path_walk
2.59% swapper [kernel.kallsyms] [k] intel_idle
2.18% perf [kernel.kallsyms] [k] __d_lookup
1.88% perf [kernel.kallsyms] [k] clear_page_c
1.60% perf [kernel.kallsyms] [k] __strncpy_from_user
1.50% perf [kernel.kallsyms] [k] system_call
1.48% perf [kernel.kallsyms] [k] dput
1.44% perf [kernel.kallsyms] [k] do_lookup
1.33% perf [kernel.kallsyms] [k] get_page_from_freelist
1.29% perf libc-2.13.so [.] 0x82715
1.19% swapper [kernel.kallsyms] [k] _raw_spin_lock_irqsave
1.11% perf [kernel.kallsyms] [k] kfree
1.10% perf [kernel.kallsyms] [k] vfsmount_lock_local_lock
1.01% perf [kernel.kallsyms] [k] __alloc_pages_nodemask
...
-------------------------------------------------------------------------------------
round 3:
Total duration 66468 s 532417 us
real: 23.35 s
user: 0.00
sys: 0.28
Events: 87K cycles
6.30% perf [kernel.kallsyms] [k] _raw_spin_lock
3.09% perf [kernel.kallsyms] [k] mutex_unlock
2.98% perf [kernel.kallsyms] [k] link_path_walk
2.98% perf [kernel.kallsyms] [k] mutex_lock
2.70% swapper [kernel.kallsyms] [k] intel_idle
2.25% perf [kernel.kallsyms] [k] __d_lookup
1.92% perf [kernel.kallsyms] [k] clear_page_c
1.56% perf [kernel.kallsyms] [k] __strncpy_from_user
1.47% perf [kernel.kallsyms] [k] dput
1.47% perf [kernel.kallsyms] [k] system_call
1.42% perf [kernel.kallsyms] [k] do_lookup
1.35% perf [kernel.kallsyms] [k] get_page_from_freelist
1.32% perf libc-2.13.so [.] 0x12902e
1.32% swapper [kernel.kallsyms] [k] _raw_spin_lock_irqsave
1.10% perf [kernel.kallsyms] [k] vfsmount_lock_local_lock
1.02% perf [kernel.kallsyms] [k] kfree
1.00% perf [kernel.kallsyms] [k] __alloc_pages_nodemask
Interesting!! Semaphore-like is almost 8s slower than mutex... Also, the Events sycles of perf
reported is different
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